1. Technical Field
The present invention relates to a method for supporting or impregnating catalytically active materials selectively on the surface of a spherical or cylindrical particulate catalyst support or in an outer pore region connected to the surface of the spherical or cylindrical particulate catalyst support using the mutual repulsive force and the solubility difference between a hydrophilic solvent and a hydrophobic solvent that are immiscible.
The present invention relates to a method for effectively reducing the production cost of a catalyst by optimizing the used amount of a noble metal to be supported or impregnated in a porous catalyst support in the fabrication process of the catalyst and, more particularly, to a fabrication method for a catalyst that involves supporting or impregnating an expensive metal or catalytically active ingredients selectively only on the surface of a porous catalyst support or in the pores in the vicinity of the surface of the porous catalyst support, thereby preventing the metal or catalytically active ingredients from being supported or impregnated in the pores in the vicinity of the center of the catalyst support that hardly participates in the catalytic reaction and thus reducing a wasteful use of the expensive metal or catalytically active ingredients.
More specifically, the present invention relates to a method for supporting or impregnating catalytically active materials selectively only on the surface of a catalyst support or in a region in the vicinity of the surface of the catalyst support having a micro-pore structure where the catalytic reaction mostly tales place, by applying a hydrophobic solvent and a hydrophilic solvent in sequence to the micro-porous catalyst support and thereby using the mutual repulsive force and the immiscibility of the hydrophobic solvent and the hydrophilic solvent. The catalyst support used in the present invention may be a spherical or cylindrical particulate catalyst support, a cylindrical particulate catalyst support with hollow pores inside the catalyst particle, or the like.
2. Description of the Related Art
In general, the catalytic reaction takes place only on the surface of catalyst particles other than inside the catalyst particles in the case of a reaction performed under the conditions involving a high space velocity, such as steam methane reforming reaction, water-gas shift reaction, and so forth. Further, in the Fischer-Tropsch reaction using catalyst particles having a particle size of 1 to 3 mm, the pore diffusion into the catalyst support is restricted in the catalyst using catalytically active materials such as cobalt (Co) or iron (Fe) supported or impregnated on the catalyst support. This can lower the production rate and the selectivity of a hydrocarbon having at least 5 carbon atoms. Therefore, the catalytically active material, if supported in the inner part of the catalyst particles in the form of pellets, possibly causes the side reactions or docs not participate in the desired catalytic reaction, ending up with deterioration in the efficiency of the catalyst.
To overcome this problem, many researchers have consistently studied and proposed a method for fabricating a catalyst that involves supporting or impregnating catalytically active materials selectively only on the surface of a formulated catalyst support, and a catalyst prepared by the fabrication method.
Korean Laid-open Patent No. 2010-0011687 discloses a method of preparing a catalyst for a catalytic reforming of carbon dioxide into methane and a reforming method using the catalyst, where the method includes the steps of immersing a silica microspore molecular sieve catalyst support in an aqueous solution of nickel nitrate, performing a drying and calcination process to complete a main catalyst, secondly immersing the catalyst into an aqueous solution of additives and then performing a second drying and calcination process to complete a final form of catalyst. This method is characterized by forming a main catalyst and additives in sequence on a single catalyst support but involves separately performing the drying and calcination process for each catalyst-forming step. This can raise the production cost of the catalyst and render the catalytically active materials still hard to support or impregnate selectively in the vicinity of the surface of the catalyst support.
Korean Patent No. 550998 suggests an electrode for fuel cell and a fuel cell system including the same, where the electrode for fuel cell includes a catalyst layer including a platinum black or platinum-transition metal alloy black catalyst having an average particle diameter of 1 to 5 nm and an electrode support including a conductive substrate.
U.S. Laid-open Patent No. 2011-0275856 discloses a cylindrical catalyst support for providing an improved ring-shaped eggshell catalyst having a shell of a catalytic oxide material applied to the outer surface, an eggshell applied to the outer surface of the catalyst support, and a preparation method for the same. In addition, U.S. Laid-open Patent No. 2003-0036476 relates to a coated catalyst having a core and at least one shell surrounding the core, a preparation method for the same, and a use of the coated catalyst and proposes a method for preparing a shell catalyst that is provided in the form of a shell attached to the surface of a cylindrical or spherical core.
However, these documents of the prior art still have some problems concerning the needs for some improvement for the sake of effective reduction of the production cost, such as an increase in the efficiency of the catalyst manufacturing process and the catalytic reaction.